A basic hearing aid comprises a microphone, speaker and audio transceiver. In such hearing aids the earpiece microphone converts acoustic waves into electrical signals representing the acoustical waves, the electrical signals are amplified and eventual processed and converted back into acoustical waves.
Remote controls with functions to control the amplification and other settings of the earpiece are often used and offer possibly wireless communicating with the earpiece. Sometimes hearing aids with remote control function have an antenna that is external connected to the earpiece.
More advanced hearing aids use wireless audio communication between the two earpieces. The method often used to establish such a communication is based on magnetic coupling. A relative large voltage, which can be 12 volts AC, is subjected to a coil which generates a magnetic field. Within a short range of this coil, the magnetic field can induce voltage in a second coil. This method provides short range voice quality communication.
When communication has to be established across a larger range, conventional solutions use a radio module that works with electromagnetic radiation. In most existing solutions such a radio module is implemented in the remote control unit. A first communication is established between the earpiece and the remote control based on magnetic coupling and a second communication is established between the remote control and further electronic equipment like cellular phone or other by means of electromagnetic radiation. Several products based on this concept are on the market; some of them use the Bluetooth standard as the second communication protocol.
One hearing aid product can be found in the market today from GN Resound, with brand name Alera. This product has an integrated antenna that is designed to operate at the 2.4 GHz ISM band intended to be used for electromagnetic radiation. This antenna occupies large areas of the hearing aid and is not able to establish communication between two hearing aids, each positioned at one ear.
Another antenna is able to communicate between two hearing aids, each positioned at one ear. However this antenna occupies large areas of the hearing aid. The antenna relies on the construction of the hearing aid like the plastic housing, or part of it, and can also use conducting parts already available at the hearing aid, like parts conducting on printed circuit boards. This kind of antenna requires each time a lot of design effort when new models of hearing aid are introduced.
Background art is disclosed in: An Analytical Path-Loss Model for On-Body Radio Propagation, G. A. Conway, W. G. Scanlon, S. L. Cotton, M. J. Bentum, 2010 URSI International Symposium on Electromagnetic Theory, or: An Antennas and Propagation Approach to Improving Physical Layer Performance in Wireless Body Area Networks, Gareth A. Conway, Simon L. Cotton, William G. Scanlon, IEEE JOURNAL on selected areas in communications, Vol. 27, NO. 1, January 2009